Abstract

We studied the interactions between atomic potassium (K) and Au(111) at a range of coverage (i.e., ΘK = 0.11–0.5 monolayer (ML)) by ab initio atomic thermodynamics. For K on-surface adsorption, we found that K energetically favors the three-fold hollow sites (fcc or hcp), while the most significant surface rumpling was obtained at the atop sites. The incorporation of gold atoms in the adsorbate layer gradually becomes energetically favorable with increasing K coverage. We proposed a possible model with a stoichiometry of K2Au for the (2 × 2)−0.5 ML phase observed in lower energy electron diffraction (LEED): one K at atop site and the other K as well as one Au adatom at the second-nearest fcc/hcp and hcp/fcc, respectively. Clear theoretical evidences were given for the ionic interaction of K on Ausurface. Additionally, phase transitions were predicted based on chemical potential equilibrium of K, largely in line with the earlier reported LEED observations: the clean surface → (√3 × √3)R30° → (2 × 2), and (2 × 2) → (√3 × √3)R30° reversely at an elevated temperature.

Received 29 October 2011Accepted 23 December 2011Published online 25 January 2012

Acknowledgments:

This work is supported by MOST under Project No. 2010CB631302 and the Fundamental Research Funds for the Central Universities, SCUT, under Project Nos. 2011ZG0017 and 2011ZM0090. The computing resources from the HPC Lab, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences (CAS), and ScGrid of the Supercomputing Center, Computer Network Information Center of CAS, are gratefully acknowledged.